I. Field of the Invention
The present invention relates to a method and a device for manufacturing a magnetic recording medium having a thin metal ferromagnetic film as a recording layer.
II. Description of the Prior Art
The coercive force of the magnetic recording medium has been increased to satisfy the needs for high-density recording. For recording and reproducing high-frequency signals, only the surface layer is magnetized. An output cannot be sufficiently increased by only an increase in coercive force.
A material which has a high saturation density of magnetic fluxes has received attention to increase the high-frequency signal output. A typical example is a medium containing a nonmagnetic material such as a binder based on the conventional coating. In this medium, ferromagnetic metal particles such as iron particles or alloy particles which have a high saturation density of magnetic fluxes are used instead of iron oxide.
Another example is a medium including a thin metal ferromagnetic film as a magnetic recording layer, which does not use a binder. Since the thin film is formed by vacuum deposition, the medium is called a "deposition tape". It is partially commercially available.
The deposition tape has been recently developed and is still in a developmental stage, so that there are many problems to be solved so as to realize wider industrial applications.
The first problem is a matter of coercive force control. Stable control of the coercive force is a significant issue in the technical developmental of the deposition tape. An oblique deposition method disclosed in Japanese Patent Publication No. 41-19389 is capable of stably controlling the coercive force. However, according to the method described above, if an angle of incidence of the material being deposited varies greatly, the change of coercive force is greatly changed; thus this method is unable to provide stable control of the coercive force.
The second problem is a matter of resistance to corrosion and abrasion of the medium. In order to solve this problem, a protective layer has conventionally often been formed on the ferromagnetic layer. However, further improvements are desired since the ferromagnetic layer and the protective layer are formed of different materials and different methods of forming the ferromagnetic layer and the protective layer are used.